Description of single-electron capture by fast multielectron ions

An analytical approximation of wave functions has been derived for the excited states of atoms and ions. The nuclear charge and the number of electrons are Z ≤ 10 and N _e ≤ 10, respectively. It is shown that the cross section of electron capture by fast ions must be estimated with allowance for their Coulomb interactions. The theoretical dependence between the single-electron capture cross section and the collision energy is close to the experimental, when ion interactions in the final state are taken into account. This proximity enables us to analyze the correlation between theoretical and experimental results.     

Electron Transitions during the Capture of an Electron by a He<Superscript>2+</Superscript> Ion at the Argon Atom

We have measured the absolute values of the total cross section of the one-electron capture by He²⁺ ions in the kinetic energy range 2–30 keV at the Ar atoms. The absolute values of the differential scattering cross sections of He⁺ ions formed during the one-electron capture and the electron capture with ionization at energies of 2.2, 5.4, and 30 keV have been determined. The electronic states of the formed ions have been determined using collision spectroscopy based on analysis of the change in the kinetic energy of He⁺ after the interaction. We have measured doubly differential (with respect to the kinetic energy and the scattering angle) cross sections of the formation of free electrons. The free electron formation channels (direct ionization and electron capture with ionization) have been analyzed by calculating the electron terms of the (HeAr)²⁺ system. The calculated cross section of capture with ionization is in conformity with the cross section measured using collision spectroscopy.     

Effect of the structure of the singly charged ion on the cross section for electron capture

The calculations of the cross section for single-electron capture by fast ions are carried out in the Oppenheimer-Brinkman-Kramers approximation. The dependences of the experimental and calculated cross sections for single-electron capture by fast singly charged ions on the collision energy coincide. This makes it possible to estimate the cross section for electron capture in the case of ion-atom collisions if experimental data are absent. The results of calculations for projectiles with filled s-type subshells show that the contribution of electron capture channels to the excited state of the scattered particle depends on the collision energy.     

One-electron capture from the inner shells in atom-multicharged ion collisions

The electron capture from the inner atomic shells by multiply charged ions at intermediate and high collision energies is considered. The cross section scaling laws, as well as the reduced energy parameter, are discussed. Universal curves for the reduced cross section versus the reduced collision energy are presented for electron capture from the K, L and M shells of Ar atoms colliding with multiply charged ions. A comparison of theoretical results with the existing experimental data is given.     

正负离子碰撞过程中电荷转移的理论研究

文中用渐近方法，采用未微扰的原子波函数，导出了正负离子碰撞过程中，当离子间的距离很大时，入射离子道与出射共价道之间的交换相互作用的解析表达式。利用该相互作用的解析表达式，并考虑在入射通道里Ｈ－离子核外有两个同科电子的情况，由多通道Ｌａｎｄａｕ－Ｚｅｎｅｒ模型分别计算了低能Ｈ＋＋Ｈ－和Ｄ＋＋Ｈ－碰撞过程中的电荷转移总截面。计算结果与已有的实验数据进行了比较。     

Ionization and single electron capture in collision of highly charged Ar16+ ions with helium

This paper uses the two-centre atomic orbital close-coupling method to study the ionization and the single electron capture in collision of highly charged Ar^16＋ ions with He atoms in the velocity range of 1.2-1.9 a.u.. The relative importance of single ionization （SI） to single capture （SC） is explored. The comparison between the calculation and experimental data shows that the SI/SC cross section ratios from this work are in good agreement with experimental data. The total single electron ionization cross sections and the total single electron capture cross sections are also given for this collision. The investigation of the partial electron capture cross section shows a general tendency of capture to larger n and l with increasing velocity from 1.2 to 1.9 a.u..     

裸核离子与中性原子碰撞电离过程的理论研究

基于处理裸核离子与中性原子碰撞电离过程的OBKN和ECPSSR理论模型,系统计算了不同裸核离子与中性原子碰撞K壳层电子俘获截面和直接电离截面,并与其它文献已有的理论和实验结果进行了比较.研究结果表明：碰撞能量较低时,电子俘获截面大于直接电离截面,随着碰撞能量的增加,电子俘获截面和直接电离截面均是先增大后减小且直接电离截面减小地非常缓慢,高能时,直接电离截面大于电子俘获截面.当入射炮弹离子速度接近0.67倍靶原子K壳层电子速度时,电子俘获截面达到最大值,而当入射炮弹离子速度接近靶原子K壳层电子速度时,直接电离截面达到最大值.     

裸核离子与中性原子碰撞电离过程的理论研究

基于处理裸核离子与中性原子碰撞电离过程的OBKN和ECPSSR理论模型,系统计算了不同裸核离子与中性原子碰撞K壳层电子俘获截面和直接电离截面,并与其它文献已有的理论和实验结果进行了比较.研究结果表明:碰撞能量较低时,电子俘获截面大于直接电离截面,随着碰撞能量的增加,电子俘获截面和直接电离截面均是先增大后减小且直接电离截面减小地非常缓慢,高能时,直接电离截面大于电子俘获截面.当入射炮弹离子速度接近0.67倍靶原子K壳层电子速度时,电子俘获截面达到最大值,而当入射炮弹离子速度接近靶原子K壳层电子速度时,直接电离截面达到最大值.     

离子碰撞过程中电荷转移的理论研究

用经典轨道蒙托卡罗(CTMC)方法计算离子与氢原子碰撞过程电荷转移截面,并计算俘获电子的n(n为主量子数)壳层分布。对于多电荷离子的碰撞过程,利用约化变量得到了截面的q标度规律。计算结果与实验测量符合得很好。     

Effect of electrons of the multiply charged ion core on single-electron capture

The population of various electronic states of particles that arise during the capture of a single electron in hydrogen and helium atoms, as well as hydrogen molecules, by Ar³⁺ and Ne³⁺ ions with an energy of several kiloelectronvolts was studied by collision spectroscopy, viz., precision analysis of kinetic energy variation for ions formed as a result of interaction between ions and atoms. It is shown that single-electron capture in many cases is a multielectron process accompanied by the rearrangement of a multiply charged ion core. It is found that the triply charged Ne³⁺ ions formed as a result of ionization of Ne atoms by electron impacts are formed mainly in metastable states. The population of excited states of particles during their multiple ionization should be taken into account in determining the characteristics of various particles by the appearance potential method. Collision spectroscopy can be used for analyzing the metastable ion impurities in ionic beams.     

Multiple ionization of argon accompanied by electron loss and capture of 0.22-6.35 MeV C^q＋ ions

In this paper a projectile ions recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22-6.35 MeV Cq^＋ （q = 1 - 4） ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization （or the single capture） of argon associated with single electron loss （or single electron capture） by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.     

Absolute cross sections for electron capture into (n, 1) subshells of N VI by VUV spectroscopic study of the N6+-He collision

Absolute cross sections for electron capture into different (n, 1) subshells have been determined for N⁶⁺-He collision at 4.2 keV/amu. The n = 3 level is predominantly populated. The total one electron charge exchange excitation cross section is deduced.     

Peculiarities in the cross sections of electron capture by phosphorus ions

The effect of decreasing the cross sections of electron capture by phosphorus (P⁵⁺) ions penetrating through gaseous media has been revealed experimentally. This effect is a violation of the known uniform dependence between the electron-capture cross section and the ion charge. Such an anomaly was not observed in measurements performed with argon ions under the same conditions. A possible reason of decreasing the cross sections of electron capture by P⁵⁺ ions may be autoionization of excited P⁴⁺ ions. The latter are formed during electron capture into excited states by metastable particles of a beam of P⁵⁺ ions.     

Influence of dynamic screening on the conductivity of hydrogen plasma including electron–electron collisions

We investigate the dynamical conductivity of dense hydrogen plasmas on the basis of the effective interaction potential (taking into account static or dynamic screening and diffraction effects). We apply a generalized Drude–Lorentz formula related to the dynamical conductivity with collision frequency. The influence of electron–ion collisions as well as the influence of both electron–ion and electron–electron collisions were taken into account via a renormalization factor. All calculations were performed on the basis of the effective potential with static or dynamic screening.     

Radiation field and resonant two-center dielectronic transitions in relativistic ion-atom collisions

We consider projectile-electron excitation and loss in relativistic collisions of ionic projectiles with excited atoms. We show that under certain conditions electron transitions in the ion and atom can be resonantly coupled in the collision via the radiation field. The resonance becomes possible due to the Doppler effect, has a well-defined impact energy threshold, and clearly manifests itself in the cross sections. Since the range of the ion-atom interaction in the resonance case is very long, the presence of other atoms in the target medium as well as the size of the space occupied by the medium have to be taken into account. As a result, the cross section may become dependent on the density of the target atoms and/or the target size.     

Si2+离子与氢原子碰撞电离过程的CTMC计算

应用经典径迹蒙特卡罗方法研究Si²⁺离子与氢原子碰撞电离反应过程.计算了随 入射离子能量变化的总截面、出射电子随角度和能量变化的一阶、二阶微分截面,及出射电子随 入射离子能量变化的平均能量.根据计算结果,讨论展示了软碰撞、电子转移到入射离子连 续态、两体相遇碰撞等电离机理,阐明了它们对碰撞总截面、微分截面、电离电子能量的影 响.通过计算出射电子到入射离子和靶的距离比的电离电子数分布研究了不同入射离子能量 “鞍点”电离机理的可能性. 关键词： 重粒子碰撞过程 经典径迹蒙特卡罗方法 电离机理     

Single electron capture in collisions of N^q＋ （q = 5, 6, 7） ions with helium

Close-coupling calculations are carried out for cross sections of the single electron capture in collisions of N^q+ (q = 5, 6, 7) ions with helium atoms in the collision velocity range from 0.3 a.u. to 1.8 a.u. The relative importances of the single ionization (SI) to the single capture (SC) are investigated for the N^q+ (q = 5, 6, 7) projectiles, respectively. The SI/SC cross section ratio for the N⁷⁺ projectile obtained from our calculations is in excellent agreement with the experimental data. The ratio curves also show us distinct behaviours when the charge of the projectile is different. The partial electron capture cross sections for different projectiles indicate that the electron on the target He atom tends to be captured by the projectile into its lower orbital of the outer shell with the decreasing projectile charge.     

质子与He+,Li++高能碰撞过程中电子俘获截面的理论计算

用OBK近似和CDW近似计算了H⁺+He⁺和H⁺+Li⁺⁺碰撞过程中电子俘获到激发态的分截面与俘获到基态分截面的比值，结果发现用OBK近似给出的比值和用CDW方法所给出的相应比值在高能区符合得很好．由此提出了一种用于计算高能H⁺与任一类氢离子碰撞的电子俘获总截面及任一激发态分截面的方法 关键词：     

低能He2+-He反应中单电子俘获微分散射过程的实验研究

利用冷靶反冲离子动量谱仪装置系统研究了20—40 keV He²⁺-He碰撞体系的态选择单电子俘获过程,实验获得了单电子俘获过程的态选择截面以及角微分截面.在所研究的能区范围,电子俘获到L壳层的截面最大,为主要的反应道,这与分子库仑过垒模型的反应窗理论的预测一致.实验测量的态选择截面与原子轨道紧耦合的计算结果很好地符合,与光谱方法的测量结果存在一定的差别,主要原因是光谱方法不能测量完整的反应通道信息.实验结果表明,总角微分截面在小角度范围主要来源于电子俘获到基态的贡献,在大角度范围主要来自电子俘获到激发态的贡献;电子俘获到基态的和激发态的角微分截面均出现振荡结构,这种振荡来源于电子俘获反应中分子轨道之间的相干效应.实验测量的角微分截面与其他实验和紧耦合方法的计算结果进行了比较和分析. 关键词： 冷靶反冲离子动量谱仪 态选择电子俘获 态选择截面 角微分截面     

激发态Li原子和基态Ar原子的相互作用势及低能弹性碰撞

在MRCI+Q/ang-cc-PCVQZ+DK理论基础上对LiAr第一激发态(A²Π)的势能曲线进行了理论计算, 采用HFD(Hartree-Fock dispersion)解析势能函数对得到的势能曲线进行拟合, 并得到了相应的光谱常数, 计算结果与实验值和大部分理论计算值符合得很好. 通过求解核运动的薛定谔方程完整地获得了每个电子态下J=0时的振动能级E_v、转动惯量B_v和6 个离心畸变常数(D_v, H_v, L_v, M_v, N_v, O_v). 然后采用分波法研究了低温及极低温度下激发态Li原子和基态Ar原子沿LiAr相互作用势的弹性碰撞, 在1.0×10^{- 12} –3.45×10^-6 eV碰撞能区内通过数值计算得到了这一弹性碰撞的总截面和各分波截面, 讨论了各分波截面对总截面的影响. 结果表明: 在入射能量低于10^-9 eV时弹性散射的总截面值很大且几乎为一常数, 总弹性截面的形状主要由s分波决定, 但是随着碰撞能量的增加, s分波对总截面的贡献不断减少, 高阶分波对散射截面的贡献逐渐增大.